控制EF数据库的创建和迁移

Question

I have an application using a EF model for the database. This application is going to run on multiple computers in the same network using one database. To make sure this works ok when there are updates. I want to control the migration and installation of the database.

I thought I could disable the EF initializer and in my application startup checks using context.database.Exists() and context.database.CompatibleWithModel if the application matches the database. If this is not the case I want to create it after I check if all client are offline.

But my problem is when I run context.database.create() , I get an error

{"Unable to update database to match the current model because there are pending changes and automatic migration is disabled. Either write the pending model changes to a code-based migration or enable automatic migration. Set DbMigrationsConfiguration.AutomaticMigrationsEnabled to true to enable automatic migration."}

What is the best approach to controlling the creation of the DB and migrates from code? And not from the initializer.

Answer 1

The problem you've got seems not related to db creation. Your model just simply does not comply any more with what migrations states. Just run add-migration script to regenerate migration files and everything should work fine. If you would like to allow automatic migrations (not required to regenerate migration classes after model changes - but generaly this is a bad idea) just set AutomaticMigrationsEnabled = true in Configuration class for migrations and this will as well fix your error. To control migrations from code the best thing you could use is DbMigrator. You use it like that:

var migrator = new DbMigrator(new MyMigrationsConfiguration());
migrator.Update();

With the Update method you can define to which migration you want to migrate your db.